IP subnet-zero , can a broadcast subnet address be used

Andrew Newman

Hi, In question 1 of the chapter 15 quiz of the CCent ICND1 book, it says that 10.43.53.255 /26 cannot be used as a host address even though the ip subnet-zero command has been configured. Earlier on in the book it says that using the ip subnet-zero command means that the subnet number and the broadcast subnet are not reserved and can be used as host IP addresses. Can anybody clear this up for me?

phoeneous

Read this: Subnet Zero and the All-Ones Subnet  [IP Addressing Services] - Cisco Systems

.255 is the broadcast of that subnet range. Although technically you could use it, it isn't recommended because of potential addressing conflicts.

Andrew Newman

Hi phoeneous, thanks for replying. If asked a similar question on the actual CCent exam, can I take it that the all-the-ones subnet is NEVER used even though the ip subnet-zero command has been configured?

prtech

10.43.53.255 is not an all-ones subnet, it's not even a subnet. It's a broadcast address, and they cannot be applied to hosts.